Abstract
Abstract
A reliable and cost-effective interconnect technology is required for the development of
hybrid pixel detectors. The interconnect technology needs to be adapted for the pitch and die
sizes of the respective applications. This contribution presents recent results of a newly
developed in-house single-die interconnection process based on Anisotropic Conductive Adhesives
(ACA). The ACA interconnect technology replaces solder bumps with conductive micro-particles
embedded in an epoxy layer applied as either film or paste. The electro-mechanical connection
between the sensor and ASIC is achieved via thermocompression of the ACA using a flip-chip device
bonder. The ACA technology can also be used for ASIC-PCB/FPC integration, replacing wire bonding
or large-pitch solder bumping techniques. A specific pixel-pad topology is required to enable the
connection via micro-particles and create cavities into which excess epoxy can flow. This
pixel-pad topology is achieved with an in-house Electroless Nickel Immersion Gold (ENIG)
process. The ENIG and ACA processes are qualified with a variety of different ASICs, sensors, and
dedicated interconnect test structures, with pad diameters ranging from 12 μm to 140 μm
and pitches between 20 μm and 1.3 mm. The produced assemblies are characterized electrically,
with radioactive-source exposures, and in tests with high-momentum particle beams. This
contribution introduces the developed interconnect and plating processes and showcases different
hybrid assemblies produced and tested with the above-mentioned methods. A focus is placed on
recent optimization of the plating and interconnect processes, resulting in an improved plating
uniformity and interconnect yield.